Mexico City — A grenade attack on Mexico's top television station during the nightly news Tuesday is the latest – and most high-profile – threat against freedom of expression in Mexico since President Felipe Calderón launched a concerted offensive against drug traffickers two years ago.

Media watch groups consider Mexico among the most dangerous places for journalists to operate. Reporters on the drug beat are increasingly the victims of intimidation as warring drug traffickers vie for power and lucrative routes into the US market.

Some 5,700 Mexicans were killed last year in drug-related violence – more than double the total from the record reached the year before. The majority of violence is between drug traffickers, but civil society – from businesses owners to bystanders, prosecutors to reporters – are increasingly victims. Many journalists now write without bylines – if they report on drug trafficking at all. And the attack on the TV station in the bustling, northern town of Monterrey, a manufacturing hub, is the latest sign that narcotraffickers don't want anyone covering their activities.

"We face a huge risk of becoming a blind and deaf country, because the messengers are not telling us what they are observing out of sheer fear," says Mexican congressman Gerardo Priego Tapia, who presides over a federal special commission on attacks against the media. "We think that this case, against the most important TV company in Mexico in one of the most important business capitals in Latin America, is not an accident. It's a symbol and a warning of how this year is going to be."

Broadcasters at Grupo Televisa reported on the attack live, as gunmen in two pickup trucks tossed a grenade and opened fire on the station in downtown Monterrey. A handwritten note left at the scene read: "Stop reporting just on us. Report on the narco's political leaders." No one was injured in the attack.

Alleged hitmen have attacked local newspaper offices across the country, some with fatal results. But this is believed to be the first attack on a TV station in Mexico.

Media rights groups condemned the assault. "Fortunately there were no victims, but this attack shows that organized crime is targeting national as well as local media," Reporters Without Borders said in a statement. "Solving this attack will be a new test for the government, which wants to make it a federal crime to use violence against the press."

Worldwide, 2008 was a safer year for traditional journalists (but tougher for online media) than 2007, according to a survey by Reporters Without Borders released in December, with 60 journalists killed, compared to 86 from the year before. Iraq ranks as the most dangerous country for journalists, with 15 killed last year, but Mexico is one of the worst. Some consider it the most dangerous country after Iraq. A study released Wednesday by the International News Safety Institute (INSI) in Belgium showed that India and Mexico followed Iraq in terms of danger for the media. They counted 10 deaths in each.

Journalists in rugged border towns such as Juárez, where a quarter of all executions tallied by the government took place last year, say they are scared. Erika, a local drug gang reporter who did not want her last name published, says she was unwillingly moved into the post after her predecessor received a death threat. "I didn't want this job, especially because my mom is so worried," she says. Sometimes she uses her byline; other times not.

Congressman Priego Tapia says the government has not paid enough attention to the plight of journalists – partially because they are part of the problem. While nearly all, if not all, of the executions of journalists are linked to organized crime, four of ten general threats, which can include breaking cameras or phone calls warning not to publish or even physical harm, come from Mexican authorities, he says.

He is pushing for a bill, struck down at the end of last year, which makes attacks against the media a federal crime. He says that organized crime groups wield too much influence over state and local investigations.

But so far, he says, the government has responded indifferently. His case in point: In December, Octavio Orellana, Mexico's special prosecutor for crimes against journalists, downplayed the threat against freedom of expression. He said that only three of 25 reporters killed in the last two years were killed directly because of their work. They are killed for the reasons "similar to what affects the rest of Mexicans," Mr. Orellana said at a press conference, referring to the overall crime rate.

Reporters Without Borders says that four Mexicans were killed last year alone in cases where there was a clear link between their deaths and their work.